Electroluminescent lamp panels are known in the art. In general, an electroluminescent lamp typically includes a base electrode spaced from a transparent electrode for sandwiching an electroluminescent or phosphorescent layer therebetween. Often a dielectric layer also is sandwiched between the two electrodes. The base electrode may be a foil layer, such as a thin aluminum foil layer, or the base electrode may be a printed layer of conductive ink. Conductive leads extend from the base and transparent electrodes of the lamp. When an AC voltage is applied across the leads, the current induced between the base and transparent electrodes causes the phosphorescent layer to emit light, a phenomenon known as luminescence. An electroluminescent lamp essentially is a light emitting capacitor having a dielectric layer between two conductive electrodes, one of which is transparent, and the dielectric layer may be a phosphorescent layer, or there may be a separate dielectric layer. The transparent electrode layer typically is made of indium tin oxide ("ITO") or indium oxide. Light is visible through the transparent electrode, and various electroluminescent chemicals are known to provide lights of various colors. Lamp panels can include one or a plurality of individual electroluminescent lamps.
In a typical electroluminescent lamp panel used as a keyboard, individual electroluminescent switch keys are used to actuate individual circuits, and individual electroluminescent lamps are associated with each key. The respective lamp may or may not be energized by the associated key. In any event, each key includes a dome-shaped actuator key mounted on top of a spacer on top of a printed circuit board which, in turn, is mounted on top of the layered or laminated electroluminescent lamp. The actuator key moves a conductive switch member through a hole in the spacer to close a gap between two circuit traces on the board. The circuit board typically is separated from the laminated electroluminescent lamp by still a further insulator. In order for the lower electroluminescent lamp to light-up the actuator key, the components of the electrical circuit, including the printed circuit board substrate, the insulator and the switch member must be light-transmissive to allow light from the subjacent electroluminescent lamp to pass therethrough. Problems with such prior art structures center around the higher costs involved in their fabrication as well as the loss of light by diffusion through the many light-transmissive components between the electroluminescent lamp and the actuator as well as blockage by opaque components.
The present invention is directed to solving these various problems by providing a unique arrangement wherein the components of the electroluminescent lamp are located immediately below a substrate, such as a dome-shaped substrate which can function directly as a switch key.